4.34 - 4.37 From wine to vinegar
Carboxylic acids are a homologous series of compounds with the functional group -CO2H.
They are all organic acids and are regarded as weak acids which means they do not ionise completely in solution.
Carboxylic acids are formed when alcohols are oxidised by the air or by using an appropriate oxidising agent. Methanol can be oxidised to methanoic acid, ethanol to ethanoic acid and so on.
Assumed background knowledge:
Students should:
- 4.34C know that carboxylic acids contain the functional group COOH
- 4.35C understand how to draw structural and displayed formulae for unbranched-chain carboxylic acids with up to four carbon atoms in the molecule, and name each compound
4.34 Activity 1 The functional group - a sting in the tail
Activity 2. 4.36C Carboxylic acid reactions
Students should:
- 4.36C describe the reactions of aqueous solutions of carboxylic acids with metals and metal carbonates
- 4.37C know that vinegar is an aqueous solution containing ethanoic acid
Carboxylic acids react in a very similar way to other acids like :
- hydrochloric acid HCl(aq)
- nitric acid HNO3(aq) and
- sulfuric acid H2SO4(aq)
In this video we see citric acid reacting with a carbonate to produce bubbles of carbon dioxide. Notice how the acid does not react until the water is added. Acids need to be aqueous to show their acidic properties.
This video shows magnesium being added to citric acid. Read the questions then watch the video all the way through and answer them carefully.